Pixel Circuit Self-Diagnosis Using Dummy and Light-Shielded Pixels
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Solution Overview
Problem
Imaging devices lack an effective self-diagnosis capability to detect malfunctions or issues within their internal circuits and connections, which can lead to operational failures and reduced image quality.
Innovation Solution
The implementation of a self-diagnosis system in imaging devices, utilizing a configuration that includes pixel circuits with accumulation units, transistors, and a diagnosis unit, which uses dummy pixels and light-shielded pixels to generate reference signals and perform AD conversion, allowing for the detection of malfunctions through comparison of digital codes generated from these signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-diagnosis function is added to imaging device, then reliability is improved, but device complexity increases
Solution Approach 1:
The imaging device is segmented into functional regions: normal imaging pixels, light-shielded pixels for reference signal generation, and dummy pixels for connection testing. This segmentation allows the self-diagnosis function to operate independently without affecting the main imaging function, thereby improving reliability while managing complexity through modular design.
Solution Approach 2:
The pixel circuits are designed with multi-functionality to serve both normal imaging operations and self-diagnosis functions. The same pixel circuit structure can operate in normal imaging mode or switch to self-diagnosis mode by activating light-shielded or dummy pixels, reducing the need for completely separate diagnostic hardware and thus limiting complexity increase.
2Measurement precision
If dummy pixels and light-shielded pixels are added for self-diagnosis, then measurement precision is improved, but area of stationary object increases
Solution Approach 1:
Instead of adding separate diagnostic components throughout the device, the patent applies local quality by creating specific regions (light-shielded pixel regions and dummy pixel regions) within the pixel array. These localized regions perform diagnostic functions without requiring changes to the entire pixel array structure, thus improving measurement precision while minimizing area increase.
Solution Approach 2:
The self-diagnosis functionality is merged with the existing pixel array structure by using light-shielded pixels and dummy pixels that share the same physical infrastructure (control lines, signal lines, and pixel circuitry). This merging approach allows malfunction detection without requiring separate dedicated diagnostic hardware, thereby improving measurement precision while constraining the increase in stationary object area.
3Reliability
If separate voltage supply lines are provided for each pixel circuit, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements preliminary action by providing separate voltage supply lines (first voltage supply line and second voltage supply line) to pixel circuits before actual imaging operations begin. This allows the self-diagnosis function to test voltage supply connections and pixel circuit functionality in advance, improving reliability by detecting connection faults before they affect normal imaging operations.
Solution Approach 2:
The patent uses dummy pixels that replicate the structure and connection pathways of normal pixels but without light-receiving elements. These copied pixel circuits allow testing of voltage supply lines and signal pathways without requiring additional physical infrastructure, thereby improving reliability for connection fault detection while limiting the increase in device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables timely detection of malfunctions and connection issues within the imaging device, improving operational reliability and image quality by performing self-diagnosis in parallel with normal imaging operations.
Implementation Method 1
each including a photodiode are disposed in a matrix, and each of the pixels generates an electrical signal corresponding to the amount of received light
Data Source
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Figure 3A~3B
AI summary
An imaging device according to the present disclosure includes: a plurality of pixel circuits; a first control line; a second control line; a first voltage supply line; a second voltage supply line; a first light-receiving element; and a diagnosis unit. The plurality of pixel circuits each includes a first terminal, a second terminal, a third terminal, an accumulation unit, a first transistor, a second transistor, and an output unit. The accumulation unit is configured to accumulate an electric charge. The first transistor is configured to couple the third terminal to the accumulation unit on the basis of a voltage of the first terminal. The second transistor is configured to supply a predetermined voltage to the accumulation unit on the basis of a voltage of the second terminal. The output unit is configured to output a signal corresponding to a voltage in the accumulation unit. The plurality of pixel circuits includes first to third pixel circuits. The first control line extends in a first direction. The first control line is coupled to the respective first terminals of the first to third pixel circuits. The second control line extends in the first direction. The second control line is coupled to the respective second terminals of the first to third pixel circuits. The first voltage supply line is coupled to the third terminal of the first pixel circuit. The second voltage supply line is coupled to the third terminal of the second pixel circuit. The first light-receiving element is coupled to the third terminal of the third pixel circuit.